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Magnum PXR and Power Defense SB low
voltage power circuit breakers user manual
Installing the drawout circuit breaker
In structures equipped for drawout circuit breakers, a bolted-in
cassette with movable extension rails supports the circuit breaker
(Figure 5 and Figure 6) . The extension rails must first be pulled all
the way out . Once the rails are fully extended, the circuit breaker
can be carefully placed on the extension rails .
m CAUTION
IT IS IMPORTANT TO TAKE GREAT CARE WHEN PLACING A DRAWOUT
CIRCUIT BREAKER ON ITS EXTENSION RAILS. IF THE CIRCUIT BREAKER IS
NOT PROPERLY SEATED ON THE EXTENSION RAILS, IT COULD FALL FROM
THE RAILS, CAUSING EQUIPMENT DAMAGE AND/OR BODILY INJURY.
Carefully lower the circuit breaker down onto the extension rails .
Be certain that the circuit breaker's four molded drawout rail
supports are fully seated in the extension rail cutouts on both
sides (Figure 6) . Do not remove the lifting yoke from the circuit
breaker until it is properly seated on the rails .
Once the circuit breaker is on the extension rails and the lifting yoke
is removed, proceed with the rest of the circuit breaker installation .
Molded rail
supports
Figure 6. One side of drawout circuit breaker properly seated on
extension rail
Rejection interlocks
Within any one physical frame size, Magnum PXR and PD-SB type
drawout circuit breakers come in a variety of continuous current
and interruption ratings, some of which are incompatible with
others . Double-wide circuit breakers also come with several phase
sequence options that are also incompatible . To prevent the insertion
of circuit breakers with (1) inadequate interrupting capability, (2)
with physically incompatible primary disconnects, or (3) with an
incompatible phase sequence, rejection interlock key plates are
provided on both the circuit breaker and the cassette . The key
plate on the circuit breaker is pre-assembled at the factory; but the
cassette-side rejection plate and the key pattern must be assembled
and installed by the switchboard builder .
DO NOT DISABLE REJECTION INTERLOCKS. DOING SO AND USING A
LOWER CAPACITY CIRCUIT BREAKER IN AN INCOMPATIBLE CASSETTE
COULD RESULT IN AN ELECTRICAL FAULT, WHICH COULD RESULT IN
DEATH, BODILY INJURY, AND/OR EQUIPMENT DAMAGE.
The rejection interlocks are steel pins in the floor of the circuit breaker
cassette . As the circuit breaker is pushed into the structure, the
mating pins on the bottom of the circuit breaker move past a set
of corresponding pins in the cassette if the circuit breaker and the
cassette are compatible . If the circuit breaker and the cassette are
mismatched, the rejection pins will block the insertion of the circuit
breaker into the cassette before the levering-in mechanism
is engaged .
Before attempting to push the circuit breaker into the DISCONNECT
position, compare the positioning of rejection interlock pins in the
cassette in keeping with those outlined in Table 1 of IL2C13863
(for MPN and SPN breakers) and/or Table 1 of IL2C15760 (for MPS
and SPS breakers), and the information supplied on the circuit
breaker's nameplate . Proceed if the circuit breaker and the cassette
are compatible .
Extension rail cutout
Figure 7. Cassette rejection interlock pin
positioning/installation
User Manual MN013016EN
Effective July 2022
m CAUTION
Stop nuts should be
torqued to 8–10 ft-lb
EATON www.eaton.com
11
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